It is well known, of course, that human sight is not perfect. Indeed, golfers can have many different sight-related problems when trying to align a golf club vis-a-vis a golf ball for the purpose of striking the golf ball into a cup. A golfer's sighting errors cause the golfer to aim incorrectly when taking a swing at a golf ball.
In the prior art, many techniques have been tried to aid golfers in aligning their golf clubs in order to strike a golf ball into a golf cup. See, for example, my prior U.S. Pat. No. 3,880,430 which proposed using a number of indicia at different levels in order to try to compensate for the sighting error of a golfer. In my prior U.S. patent, I used a sighting line which was aligned exactly perpendicular to the ball-striking face of the club.
Others recognized that one way of compensating for human sighting errors was to place the sighting line at some angle, other than perpendicular, to the ball-striking surface. See, for example the disclosure of U.S. Pat. No. 3,826,495 to Elkins, the disclosure of which is hereby incorporated herein by reference. The method and apparatus disclosed by Elkins sufferers from a number of drawbacks. One drawback of the Elkins device is that each club head is inscribed with a corrected sighting line and if a golf-pro shop or other store for selling golfing equipment is to carry a reasonable selection of goods, the fact that any given golf head can have a large number of possible sight correction lines associated with it, causes stocking problems for golf clubs to increase manyfold. The present invention overcomes this difficulty in that the sighting line on the golf club may be adjusted, in accordance with the needs of a particular golfer, at the time the golf club is sold to the golfer. A further drawback of the Elkins device is that it is limited to a golf club head with a broad top surface. The present invention overcomes this difficulty by allowing the corrected sighting line to be applied to a wide variety of club head shapes.